Beneficial effect of steroid on myocardial preservation in isolated rat hearts

Myocardial injury after heart storage has been known to contribute to an increase in myocardial calcium content or oxygen free radical production. The present experiment was designed to determine the inhibitory effect of steroid in the preservation solution on myocardial injury during simple immersion of isolated rat hearts. The experimental group was divided into 5 sub-groups according to the concentration of steroid added to the solution. Group I was stored in preservation solution containing no steroid. Groups II to V were stored in preservation solutions containing methylprednisolone in concentrations of 50 mg/L, 100 mg/L, 150 mg/L, and 200 mg/L, respectively. After the rat hearts were isolated, crystalloid cardioplegic solution at 4 degrees C was used for cardiac arrest, and the hearts were immersed in 4 degrees C Euro-Collins solution for 8 h. Hearts were then maintained under ischemic conditions at 25 degrees C for 15 min. After 60 min of reperfusion at 37 degrees C, cardiac function was measured and biochemical analyses of coronary effluent and myocardium were performed. The cardiac outputs in groups IV and V were significantly higher than those in groups I and II (p < 0.01). Creatine kinase-MB in coronary effluent in groups IV and V were significantly lower than those in groups I and II at 15, 30 and 60 min after reperfusion (p < 0.05). The level of arachidonic acid at 1 and 5 min, and the level of malondialdehyde at 5 min, after reperfusion in groups III, IV and V were significantly lower than those in groups I and II. Myocardial adenosine triphosphate was most preserved in group IV, and myocardial arachidonic acid, malondialdehyde, and calcium levels and water content in groups IV and V were lower than those in groups I and II. Ultrastructural observations also showed that myofilaments and mitochondria were well preserved in groups III, IV and V at 15 min after reperfusion compared with those in groups I and II. These results indicate that the addition of steroid to preservation solution might be effective in preventing myocardial injury during preservation of rat hearts, and the optimal concentration appears to range from 150 mg/L to 200 mg/L.